Time alignment of drivers

[Leo11]

I'm trying to figure out the best solution to adopt for my multi-way system.
From the Audiolense XO demo I saw that the software takes care of aligning the drivers, however I would like to understand better which method it uses.
In particular I would like to understand if the alignment is based only on the measured impulse response, or if it is performed applying phase linearization (and possible polarity correction) of the drivers.

 

[juicehifi]

Peak identification comes first. Polar correction comes next unless disabled. Next out is peak alignment, which accounts for the peak after correction and XO. And we’re dealing with a different peak than the one we started with. Lastly, a phase alignment, that may alter the timing if needed. Most of the time, with linear phase XO, the peak alignment is practically spot on.

The time alignment of drivers has been optimized through extensive empirical testing, using measurements from various users.

 

[Leo11]

Peak identification comes first. Polar correction comes next unless disabled. Next out is peak alignment, which accounts for the peak after correction and XO. And we’re dealing with a different peak than the one we started with. Lastly, a phase alignment, that may alter the timing if needed. Most of the time, with linear phase XO, the peak alignment is practically spot on.

The time alignment of drivers has been optimized through extensive empirical testing, using measurements from various users.

Thanks Bernt, almost clear.
What exactly does the bold phrase mean?

 

[juicehifi]

It means matching the phase at the crossover point.

 

[kevinzoe]

If I may piggy-back a driver time alignment situation and question on this thread . . .
My measurements with AL XO consist of two bi-amped main speakers and two identical subs, so 6 measurements in total. I noticed that the closest sound source to the mic was one sub which correctly measured a delay of 0ms. But the second sub just 42" (107cm) further away from the first sub has a delay of over 5ms which seemed excessive. So, I played music and the bass wasn't as tight sounding and slightly behind the beat especially noticeable on reggae music.

This may be sacrilegious but I manually changed the second sub's delay to 4ms (keeping all others unchanged), saved the measurement, re-filtered and regenerated the correction filter and re-listened to the music. Better, but 3ms was spot on!

So, might this sub's measurement quality been off due to being next to a couch that may have played havoc with the measurement, or because it was facing into the back wall corner so the sound exited the sub struck the back wall then bounced back towards the mic?

I'm curious if anyone else has manually over ridden the driver delay to better affect because of some weird thing happening to the measurement quality. I doubt this is any software bug just to be clear - it's more likely reflection and couch absorption issues I'm guessing. I welcome your thoughts . . .

 

[BenToronto]

Time alignmen never made much difference to my system (and certainly none on music) and I am talking about big Klipschorn-level mis-alignment. Even polarity alignment of multiple subs always resulted in various gains and losses.

Sounds like a necessary idea and loads of fun with DSP (that nobody should be without today). Until you give a few seconds of thought to XOs, chair locations, room acoustics, how music differs from sine-wave testing, etc.

Getting FR OK at your one seat is prolly as far as you can hope to engineer by adjusting the knobs on your DSP (XO, slope, polarity, time...) pending final tuning by ear.

B.

 

[Luffy123]

Peak identification comes first. Polar correction comes next unless disabled. Next out is peak alignment, which accounts for the peak after correction and XO. And we’re dealing with a different peak than the one we started with. Lastly, a phase alignment, that may alter the timing if needed. Most of the time, with linear phase XO, the peak alignment is practically spot on.

The time alignment of drivers has been optimized through extensive empirical testing, using measurements from various users.

Dear Bernt,
does your peak alignment work even with drivers that cover different frequencies range, for example a sub and a main unit? I'm asking this because in a JBL webinar ("Subwoofer Alignment with Full-Range Systems in the Time Domain with Charlie Hughes" on youtube) it seems that we need to align the initial energy arrival instead of peaks. Could you please clarify this aspect? Thank you very much.

 

[juicehifi]

Yes, everything is time aligned